Why valve checks are an essential part of summer maintenance
Fraser Higgins, Durapipe UK industrial product manager, explains why valves should not be overlooked as part of the summer maintenance programme within water treatment facilities
The summer shutdown season is now upon us, which is the time that many water and wastewater processing facilities receive their annual inspection and maintenance programme.
However, rather than purely checking this equipment, plant and maintenance managers should take the opportunity to ensure products are still meeting the requirements of the application.
While larger equipment such as chemical tanks, pumps and pipelines will be thoroughly inspected during this period, valves – which are integral to the successful operation of these facilities – should not be overlooked.
It may seem obvious, but the first check should always be to see if there are any leaks in the valve. Initial indications that a valve is leaking could be when build up on the valve ends, or around the handle, can be seen. This is often mistaken for dirt and ignored but, in warm environments, this can sometimes be liquid that has leaked and evaporated, leaving a crystalline deposit.
It is important that any deposits, even if they are believed to be dirt, are thoroughly checked. The best way to undertake this is to remove the valve from the system and inspect the seals, which are the most vulnerable areas.
When seals age and decay, they can begin to leak. In some cases it may be possible to replace the seals, but it is always worth considering replacing it with a new valve where necessary. Valve designs vary and, to ensure system integrity, it may be worth selecting a valve that has an increased number of seals, offering increased protection against leaks.
Movement within a valve can also contribute to leakage. The key area susceptible to movement is around the union nuts, which can become loose if there is aggressive vibration in the system. As an immediate fix, these can be tightened to the correct position, but if it becomes an ongoing problem, changing to a valve with a locking mechanism, which keeps the nut held steady, should be considered.
It is also important to consider whether there have been any changes in the process, such as temperature, pressure or acidity, since the system was originally specified. These factors significantly affect the integrity of the system, and place stress on the component parts, so if there have been changes it is crucial to check that the equipment and valves in use are still fit for purpose.
Manufacturer technical support teams should always be consulted to provide advice on the most appropriate valves for use with new temperatures, fluids and pressures.
If plant and operation managers are experiencing frequent ‘jamming up’ of ball valves, it could be due to the sediment present in a process. A simple way to address this, without needing to replace the valve, is to fit sediment strainers into the line. The latest versions offer a range of filtration meshes, in different materials to avoid corrosion, while benefitting from easy maintenance.
Alternatively, to avoid adding new elements into the process, the ball valves can be replaced with a diaphragm valve, which works by a rubber seal closing the valve, meaning it is not as likely to become blocked from sediment as a ball valve.
The planned summer shutdown is the ideal time to look at the control of flow in a system and whether the required flow is being achieved. Ball valves are the most common valve installed to control flow; however, they do have limitations with the accuracy of flow that can be delivered and users often simply open the valve approximately a quarter or half turn depending on the flow required.
If accurate flow regulation is required, a simple change to a metering ball valve that can offer a graduated positioning indicator will meet the requirements.
Increasingly, industrial processes require valves to be operated remotely as a safety measure, to reduce downtime and to increase efficiency, but this does not mean the existing valves need to be replaced, which is a common misconception.
Actuators can be retrofitted to existing valves, minimising disruption to the plant operation, while benefiting from the ability to be able to operate valves remotely, immediately and safely.
Finally, when reviewing the system, it is paramount to check the products still meet legislation given that they may have changed or been updated since the system was installed, which is of particular importance due to utility companies tightening the requirements on what can be put back into the water system.
The discharge of trade effluent into the public sewer system is governed by the Water Industry Act 1991, with individual water utilities setting the legal limits within their area. It is a criminal offence to breach these limits, with prosecution and significant fines likely to be enforced if companies are found guilty of exceeding set limits.
To ensure compliance, in line pH, conductivity, and ORP (redox) measurement devices can be installed.
These can be simply introduced into an existing system by using an installation tee or a clamp saddle, depending on pipe size. For processes that already have these in place, it is important to check that there is no corrosion, software is up to date and that they have been programmed correctly.
If planned maintenance and inspection reveals that valves have become damaged or no longer meet the requirements of the application, plant managers should consider replacing the valve.
Replacement may incur more cost than a simple repair initially but will provide a more cost-effective solution over the lifetime of the system, due to avoiding unplanned maintenance or stoppages, not only ensuring the long-term security of the network but allowing it to cater for any future changes in the system.
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